Tandy 1000 Programmer's Reference Guide

Chapter 1 I System Calls
Terminate But Stay Resident
Interrupt 27H
Used to make a piece of code remain resident in the sys-
tem after its termination. This call is typically used in
.COM files to allow some device-specific interrupt handler
to remain resident to process asynchronous interrupts.
When Interrupt
27H is executed, the program terminates
but is treated as an extension
of MS-DOS. It remains res-
ident and is not overlaid by other programs when it
terminates.
This interrupt provides compatibility with earlier versions
of MS-DOS. New programs should use the function 31H,
Keep Process.
Entry Conditions:
CS:DX = first byte following last byte of code in the
Macro Definition:
program
stay-resident macro last-instruc
mov dx,offset last-instruc
inc dx
int
27H
endm
Example:
;CS must be equal to PSP value5 given at program start
;(ES and DS values)
rnov DX,LastAddress
int
27H
;There is no return from this interrupt
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Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200